1. Field of the Invention
The present invention relates to the next generation mobile communications, and more particularly, to a rate matching method for the next generation mobile communication system.
2. Background of the Related Art
The ARIB of Japan, ETSI of Europe, T1 of U.S.A., TTA of Korea and TTC of Japan mapped out a more advanced next generation mobile communication system based on a radio access technique and a core network technique of the existing global system for mobile communications (GSM) that services multimedia such as sound, an image and data. The parties agreed with joint researches to present a technical specification for the advanced next generation mobile communication system, and the project was called a third generation partnership project (hereafter “3GPP”).
The 3GPP is classified into several technical specification groups (TSG). In a research field for a radio access network (RAN) among the TSGs of the 3GPP, a technical specification for an uplink rate matching and a downlink rate matching is provided. The rate matching is realized by adjusting to a code rate level most appropriate to a radio interface through a puncturing process for removing a specific bit or a repetition process for adding a specific bit for a bit stream provided via a channel coding.
Algorithms used in the rate matching can be divided into puncturing algorithms and repetition algorithms. Further, different rate matching algorithms are embodied in an uplink and a downlink, which is the reason why an interleaving for a rate matched bit stream is performed in the downlink and a rate matching for an interleaved bit stream is executed in the uplink.
FIG. 1 is a block diagram showing the structure for an uplink in a conventional 3GPP standard. In the uplink, data streams of several transport blocks having the same quality of service (hereafter “QoS”) have a channel coding execution according to a desired code rate, and then, are branched off into several sequences. These sequences are passed through a procedure of a 1st interleaving in a unit of a code symbol. Such 1st interleaved sequences undergo the rate matching using the puncturing algorithm or the repetition algorithm.
FIG. 2 represents a block diagram showing the structure for a downlink in the conventional 3GPP standard. In the downlink, data streams of several transport blocks having the same as ‘QoS’ have a channel coding execution according to a required code rate, and then, are branched off into several sequences. The sequences of the respective branches undergo rate matching using the puncturing algorithm or the repetition algorithm. Such rate matched sequences have an execution of a 1st interleaving in a unit of a code symbol.
In the channel coding applicable to the transport channel (TrCH) of the uplink or downlink there is a convolutional coding and a turbo coding. However, other specific channel coding may be applied thereto.
A multi-stage interleaver (MIL) is used as an interleaver for performing the 1st interleaving in this uplink or downlink. For reference, the span of the 1st interleaving using the MIL is same as a transmission time interval (TTL) of the TrCH.
The MIL writes a bit stream on an interleaver memory in a unit of a row, reads it in a unit of a column, and constructs an output bit stream. At this time, it is characterized that a rule based on a bit reversing order is applied in an order of reading the interleaver memory.
For example, if the number of column for the 1st interleaver is 8, each column number can be represented with 3 digits. Bit reversing for the column number can be performed in such a way that the column number bit value is reversed, namely, in such a method as ‘0(000)->0(000)’, ‘1(001)->4(100)’, ‘2(010)->2(010)’, ‘3(011)->6(110) etc. and thereby the column bit stream based on an order of “0 4 2 6 1 5 3 7” is outputted by 1st MIL interleaver, instead of an output of the column bit stream based on an order of “0 1 2 3 4 5 6 7”.
The following table 1 represents the order of the column bit stream outputted from the MIL on the basis of respective columns of the interleaver.
TABLE 1R(k)KR(0)R(1)R(2)R(3)R(4)R(5)R(6)R(7)20140213804261537Table 1 shows bit reversing when the number of columns (k) of the interleaver is 2, 4 and 8, respectively, and where R(k) indicates a result of a bit reversing.
FIG. 3 provides an order of the column bit stream outputted from the MIL in case that the column number of the interleaver, K, is 8 as shown in Table 1, in an example. Digits represented in shadow blocks of FIG. 3 indicate the order of the column bit stream actually outputted from the interleaver.
One code symbol in a turbo coder is constructed with a systematic bit, a 1st parity bit and a 2nd parity bit. The first parity bit represents output bits of an upper Recursive Systematic Convolutional Coder (RSC coder), and the second parity bit indicates output bits of a lower RSC coder. In contrast to the convolutional code, in the turbo code an importance of the three bits constructing the code symbol is different among one another.
In other words, among the systematic sequence, the 1st parity sequence and the 2nd parity sequence turbo-coded and branched off, the systematic sequence is relatively important and the remaining parity sequences decrease in importance, when decoding. Therefore, a method is needed for excluding the puncturing for the systematic sequence and puncturing mutually equally only for the remaining parity sequences, in the puncturing technique for the turbo code.
A conventional puncturing algorithm for the turbo code in the downlink is described in the following. For the turbo code in the downlink, the puncturing is generated in a unit of a code symbol, differently from the convolutional code basically generating the puncturing in a unit of a code bit.
One example out of the puncturing algorithms for the turbo code in the downlink provides that a puncturing position of the code symbol unit is decided so as to constantly perform the puncturing in the code symbol unit, and after that, the parity sequences on a corresponding code symbol position are alternately punctured. In another puncturing algorithm for the turbo code in the downlink, a position having the puncturing occurring in the code symbol unit is extended by twice distance, and after that, the parity sequences are simultaneously punctured every a code symbol in which each puncturing occurs.
Such puncturing algorithms for the turbo code are considered in the downlink. Since the puncturing procedures for the turbo code of the downlink occurs before the interleaving, the puncturing can be performed independently from the interleaving procedure.
However, if the puncturing algorithm for the turbo code are considered in the uplink, the puncturing procedure for the rate matching should be performed after the interleaving. Thus, additional terms need to be considered in comparison with the downlink.
As described above, the related art uplinks and downlinks in the 3GPP standard have various disadvantages. That is, parameters used in the puncturing procedure for the turbo code in the downlink cannot be used as is, and other and/or additional parameters should be used to satisfy a uniform puncturing of a code bit unit having a consideration for the interleaving. In other words, for a uniform amount for the respective interleaved column bit stream to be punctured, parameters are needed so that the puncturing may be uniformly generated even for the bit stream before the interleaving.
However, it is the present situation such a puncturing technique for such turbo code of the uplink is not yet considered and needed. Further, when the parameter used in the existing downlink is used in the uplink without change, even in the repetition procedure for the turbo code, a problem is caused that only a stream of a specific row is repeated. Also, it is the present situation that a rate matching method is needed that is applicable to all of a channel code such as the turbo code and the convolutional code etc. and channel codes used in the uplink and downlink.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.